Current treatments for type 1 diabetes (T1D) focus on insulin replacement. We demonstrated the therapeutic potential of a secreted protein fraction from embryonic brown adipose tissue (BAT) that mediates insulin receptor-dependent recovery of euglycemia in a T1D, nonobese diabetic (NOD) mouse model, by suppressing glucagon secretion. This fraction promoted white adipocyte differentiation and browning, maintained healthy BAT, and enhanced glucose uptake in adipose tissue, skeletal muscle, and liver. We identified nidogen-2 as a critical BAT-secreted protein that reverses hyperglycemia in NOD mice, inhibits glucagon secretion from pancreatic α-cells, and mimics other actions of the entire secreted fraction. Secretions from a BAT cell line with siRNA knockdown of nidogen-2 failed to inhibit glucagon secretion and restore euglycemia. These findings demonstrate that BAT-secreted peptides represent a novel therapeutic approach to diabetes management. Furthermore, our research reveals a novel signaling role for nidogen-2 beyond its traditional classification as an extracellular matrix protein.

Cadaveric islet and stem cell-derived transplantation hold promise as treatments for type 1 diabetes. To tackle the issue of immunocompatibility, numerous cellular macroencapsulation techniques that use diffusion to transport insulin across an immunoisolating barrier have been developed. However, despite several devices progressing to human clinical trials, none have successfully attained physiological glucose control or insulin independence. Based on empirical evidence, macroencapsulation methods with multilayered, high islet surface density are incompatible with on-demand insulin delivery and physiological glucose regulation when solely reliant on diffusion. An additional driving force is essential to overcome the distance limit of diffusion. In this study, we present both theoretical evidence and experimental validation that applying pressure, at levels comparable to physiological diastolic blood pressure, significantly enhances insulin flux across immunoisolation membranes, increasing it by nearly three orders of magnitude. This significant enhancement in transport rate allows for precise, subminute regulation of both bolus and basal insulin delivery. By incorporating this technique with a pump-based extravascular system, we demonstrate the ability to rapidly reduce glucose levels in diabetic rodent models, replicating the timescale and therapeutic effect of subcutaneous insulin injection or infusion. This advance provides a potential path toward achieving insulin independence with islet macroencapsulation.

Diabetic peripheral neuropathy (DPN) is a common diabetes complication with no currently available curative treatments. Here, we demonstrated that the protein level of G-protein-coupled receptor 40 (GPR40) is significantly repressed in the sciatic nerves (SNs) of DPN patients, as well as in the peripheral nerves, including dorsal root ganglia (DRG) and SNs, of streptozotocin-induced type 1 diabetic mice and BKS Cg-m+/+Lepr db/J (db/db) type 2 diabetic mice. We identified that amlodipine besylate (AB), a first-line clinical antihypertensive drug, is a GPR40 agonist capable of alleviating DPN-like pathologies in mice. These pathologies include neurological damage, destruction of myelin sheath structures, vascular injury, loss of intraepidermal nerve fibers, and impaired neurite outgrowth in DRG neurons. To elucidate the underlying mechanisms, we generated the DPN mice with GPR40-specific knockdown in SN and DRG tissues using adeno-associated virus 8-GPR40-RNAi. Mechanistically, AB attenuated inflammatory responses via the GPR40/β-arrestin2/NLRP3 pathway and ameliorated mitochondrial dysfunction through the GPR40/LKB1/AMPK/SIRT1/PGC-1α pathway in DPN mice, which were all further validated in primary human Schwann cells. Additionally, AB suppressed the cross talk between Schwann cells and endothelial cells/DRG neurons in DPN mice. Collectively, our findings highlight the potential of AB for the treatment of DPN.

Revascularization strategies failed to improve outcome in patients with diabetes with peripheral artery disease (PAD). Histone modifications are key modulators of gene expression and could play a role in angiogenic response. This study investigates the role of chromatin remodelling in modulating angiogenesis in diabetes. RNA sequencing (RNA-seq), and angiogenic assays (cell migration and tube formation) were performed in human aortic endothelial cells (HAECs) exposed to normal glucose (NG, 5 mmol/L) or high glucose (HG, 25 mmol/L) for 48 h. The expression of the histone methyltransferase SETD7 and its chromatin signature at histone 3 on lysine 4 (H3K4me1) were investigated by Western blot and chromatin immunoprecipitation (ChIP). Diabetic mice were treated with the SETD7 inhibitor (R)-PFI-2 or vehicle and underwent hind limb ischemia by femoral artery ligation. The experimental findings were translated into two cohorts of patients with diabetes with PAD. RNA-seq in HG-treated HAECs unveiled SETD7 as the top-ranking transcript. SETD7 upregulation was associated with increased H3K4me1 levels and defective angiogenesis. Both SETD7 depletion and (R)-PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-induced H3K4me1 enables the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA3G) by increasing chromatin accessibility to peroxisome proliferator-activated receptor-γ. In diabetic mice with hind limb ischemia, (R)-PFI-2 improved limb perfusion by suppressing SEMA3G. The SETD7/SEMA3G axis was upregulated in patients with diabetes with PAD. Of note, (R)-PFI-2 restored angiogenic properties in endothelial cells collected from patients with diabetes. These findings show that SETD7 is a druggable epigenetic target in diabetic PAD.

The association between KCNJ5 mutations and the risk of developing new-onset diabetes (NOD) in patients with unilateral primary aldosteronism (uPA) remains underexplored. To investigate this association, we conducted a longitudinal study using data from the Taiwan Primary Aldosteronism Investigation database. Our sample included 360 patients with uPA who underwent adrenalectomy between 2012 and 2017, 191 (53.1%) of whom had KCNJ5 mutations in their adrenal adenomas. We found that patients with uPA harboring KCNJ5 mutations had a higher rate of complete clinical success (69.5% vs. 43.8%; P < 0.01) and complete biochemical success (93.8% vs. 86.6%; P = 0.04) compared with those without KCNJ5 mutations at 6 months to 1 year after adrenalectomy. Over an average follow-up period of 8.5 years, multivariate Cox regression analysis revealed that patients with uPA with KCNJ5 mutations had a significantly lower risk of developing NOD (hazard ratio [HR] 0.41; 95% CI 0.17-0.996; P = 0.049). Additionally, we identified higher BMI (HR 1.23; 95% CI 1.11-1.37; P < 0.01) and lower estimated glomerular filtration rate (eGFR; HR 0.98; 95% CI 0.97-0.99; P = 0.01) as potential predictors of NOD based on baseline characteristics. The association between patients with uPA without KCNJ5 mutations and higher incidence of NOD was less pronounced in subgroups characterized by younger age, higher BMI, higher eGFR, and lower potassium levels. In conclusion, patients with uPA without KCNJ5 mutations had a higher incidence of NOD, with 13.6% affected during long-term follow-up. Our findings suggest that patients with uPA without KCNJ5 mutations may require more frequent follow-up for NOD after adrenalectomy.

Obesity in childhood is associated with adulthood obesity, type 2 diabetes (T2D), and future metabolic complications. The gut microbiota is a modifier of host metabolic function with altered bacterial composition associated with disease risk. Few studies have investigated the relationships among metabolic disease, inflammation, and the gut microbiota in youth, in whom these connections likely originate. Here, we characterized the gut microbiome of a cohort of 56 adolescents with obesity and without diabetes using fecal DNA sequencing with absolute bacterial quantitation together with immune and metabolic profiling. We observed multi-log order variation in absolute bacterial biomass dependent on host environment and associated with bacterial taxonomic composition based on a nested case-control comparison. Participants with higher biomass displayed a healthier phenotype with higher gut microbiome diversity; lower abundance of taxa associated with inflammation and pathogenicity, such as Escherichia coli; and lower levels of neutrophil activities. Further association analysis revealed sex-dependent variation, with higher levels of insulin resistance, fasting triglycerides, and markers of neutrophil activities in male adolescents with lower bacterial biomass. Together, these results suggest that intestinal bacterial biomass and composition are associated with metabolic and inflammatory dysregulation evident before T2D diagnosis and identify sex differences in microbiome-associated metabolic dysfunction in adolescents with obesity.

The discovery and development of the radioimmunoassay (RIA) for insulin by Berson and Yalow fundamentally changed biomedical science. The story of this accomplishment began with the pairing of brilliant scientists with complementary expertise who identified a key gap in knowledge they were able to bridge through a series of insightful experiments. Through a succession of important publications over 5 years of work, Berson and Yalow refined the approach to a novel method to measure insulin and demonstrated the power of this method in convincing clinical studies. This culminated in 1960, with three independent papers introducing the insulin RIA and demonstrating the utility in measuring circulating insulin in healthy and diseased states. Two of these papers were published in Diabetes-classics that are revisited here.

The unfolded protein response (UPR) drives events that promote diabetic retinopathy, including vascular endothelial growth factor (VEGF) upregulation in Müller cells. How UPR is activated in vivo in the diabetic retina is not well understood. CD40 is required for development of diabetic retinopathy, but whether CD40 mediates activation of UPR sensors is unknown. CD40 ligation in Müller cells caused phospholipase Cγ1 (PLCγ1)-dependent activation of UPR sensors (PERK, IRE1α, and ATF6α) and VEGF production dependent on PLCγ1 and UPR sensors. Diabetic Cd40-/- mice did not exhibit UPR activation or VEGF upregulation in the retina. These responses were restored in diabetic Cd40-/- mice rescued to express wild-type CD40 in Müller cells but not in mice rescued to express a CD40 mutation unable to recruit TRAF2/3. Intravitreal administration of a cell-permeable CD40-TRAF2/3-disrupting peptide reduced UPR activation, VEGF upregulation, and vascular leakage in diabetic mice. CD40 and TRAF2 in Müller cells from patients with diabetic retinopathy colocalized with activated UPR sensors and VEGF. Our study indicates that CD40 (via TRAF2/3 signaling) is an inducer of UPR activation that triggers VEGF production in Müller cells. This work uncovered inhibition of CD40-TRAF2/3 signaling as a potential approach to impair UPR activation, VEGF upregulation, and vascular leakage in diabetic retinopathy.

Diabetic neuropathic pain is associated with elevated plasma levels of methylglyoxal (MGO). MGO is a metabolite of glycolysis that causes pain hypersensitivity in mice by stimulating the phosphorylation of eukaryotic initiation factor 2α (p-eIF2α) and subsequently activating the integrated stress response (ISR). We first established that Zucker diabetic fatty rats have enhanced MGO signaling, engage ISR, and develop pain hypersensitivity. Since nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the expression of antioxidant proteins that neutralize MGO, we hypothesized that fumarates, like diroximel fumarate (DRF), will stimulate Nrf2 signaling, and prevent MGO-induced ISR and pain hypersensitivity. DRF (100 mg/kg) treated animals were protected from developing MGO (20 ng) induced mechanical and cold hypersensitivity. Mechanistically, DRF treatment protected against MGO-induced increase in p-eIF2α levels in the sciatic nerve and reduced loss of intraepidermal nerve fiber density. Using Nrf2 knockout mice, we demonstrate that Nrf2 is necessary for the antinociceptive effects of DRF. Cotreatment of MGO (1 µmol/L) with monomethyl fumarate (10, 20, and 50 µmol/L), the active metabolite of DRF, prevented ISR in both mouse and human dorsal root ganglia neurons. Our data show that targeting Nrf2 with DRF is a strategy to potentially alleviate pain associated with elevated MGO levels.

Microbial signals trigger the release of neutrophil extracellular traps (NETs) through peptidyl arginine deiminase 4 (PADI4). In turn, NETosis can propagate inflammation to distant tissues. We hypothesize that PADI4 mediates the interactions between diet-modified microbiota and host metabolism. We report that in the adipose tissue of individuals with obesity, NETosis was associated with dysglycemia. In mice, high-fat diet (HFD) induced not only dysmetabolism and metainflammation but also local and systemic signs of NETosis. Deleting Padi4 in hematopoietic cells (Padi4KO) blunted liver and adipose inflammation and improved metabolism under HFD. While NETs were able to disrupt gut epithelial integrity, abrogating NETosis preserved intestinal barrier function and mitigated metabolic endotoxemia due to HFD. Padi4 deletion did not prevent diet-induced dysbiosis, but Padi4KO mice were protected from intestinal hyperpermeability and metabolic impairment due to the transfer of HFD-modified microbiota. As Padi4KO did not blunt the dysmetabolic effects of lipopolysaccharide, we concluded that NETosis operates at the microbiota-intestinal interface, inducing hyperpermeability and the systemic spillover of bacterial-derived products, paving the way to the metabolic consequences of HFD. Finally, pharmacologic PADI4 inhibition recapitulated findings obtained in Padi4KO mice on metabolism and liver steatosis, thereby uncovering a druggable role for PADI4 in mediating the metabolic effects of unhealthy microbiota.

Anti-vascular endothelial growth factor (anti-VEGF) therapies are effective treatment for severe diabetic retinopathy (DR) and macular edema, but a significant subset of people had inadequate response to anti-VEGF intervention. Because elevation or overexpression of retinol binding protein 3 (RBP3) decreases risks for retinal pathologies and progression to severe DR, we compared the therapeutic profiles of RBP3 and anti-VEGF antibody to normalize retinal dysfunctions induced by diabetes. Intravitreous injection of recombinant human RBP3 (rhRBP3) and anti-VEGF antibody (namely, bevacizumab) inhibited retinal vascular permeability in Lewis rats induced by VEGF-A or after 2 months of diabetes induced by streptozotocin, in parallel with reductions of retinal VEGF and VEGF receptor 2 expressions and tyrosine phosphorylation of VEGF receptor. Only rhRBP3 ameliorated diabetes-induced reduction of neural retinal function, measured by electroretinogram. Furthermore, rhRBP3 reduced retinal expressions of inflammatory cytokines (TNF-α and IL-6) in retinal pigmented epithelial and Müller cells exposed to hyperglycemia. Metabolic studies, using a Seahorse flux analyzer, showed only rhRBP3 normalized retinal glycolytic rates in diabetic rats. Thus, both intravitreous anti-VEGF antibody and RBP3 injections normalized retinal vascular dysfunctions caused by diabetes. Only RBP3 targeted both neural and vascular retina to reduce glycolytic rates, reverse neural-retinal dysfunctions, and reduce inflammatory cytokines induced by diabetes, to delay early changes of DR.

Finding no head-to-head research evaluating the cardiovascular and renal benefits of sodium-glucose cotransporter 2 inhibitors (SGLT-2i) and glucagon-like peptide 1 receptor agonists (GLP-1RA) in patients with type 2 diabetes (T2D) at different baseline renal function, we performed a network meta-analysis to compare the two drugs indirectly. Systematic literature searches were conducted of the PubMed, Cochrane Library, Web of Science, and Embase databases, covering their inception until 7 January 2025. Randomized controlled trials (RCTs) comparing the effects of SGLT-2i and GLP-1RA in T2D with different glomerular filtration rates (eGFRs) were selected. Results were reported as risk ratios (RRs) with corresponding 95% CIs. Finally, 10 RCTs involving 87,334 patients with T2D were included. In patients with an eGFR >90 mL/min/1.73 m2, GLP-1RA exhibited a superior ability to reduce the risk of all-cause death compared with SGLT-2i (RR 0.75; 95% CI 0.58, 0.97), but it was less effective in reducing the risk of renal outcome (RR 1.80; 95% CI 1.15, 2.84) in patients with an eGFR 60-90 mL/min/1.73 m2. Conversely, in patients with eGFR 30-60 and 60-90 mL/min/1.73 m2, GLP-1RA did not show an advantage in reducing the risk of hospitalization for heart failure (RR 1.87 [95% CI 1.15, 3.04] and 1.37 [95% CI 1.05, 1.78], respectively).

Sodium-glucose transporter-2 inhibitor (SGLT2i) drugs are widely used for lowering blood glucose levels independent of insulin. Beyond this, these drugs induce various metabolic changes, including weight loss and impaired bone integrity. A significant gap exists in understanding SGLT2i-induced skeletal changes, as SGLT2 is not expressed in osteoblasts or osteocytes, which use glucose to remodel the bone matrix. We studied the impact of 1, 3, or 6 months of canagliflozin (CANA), an SGLT2i treatment, on the skeleton of 6-month-old genetically heterogeneous UM-HET3 mice. Significant metabolic adaptations to CANA were evident as early as 1.5 months after treatment, specifically in male mice. CANA-treated male mice exhibited notable reductions in body weight and decreased proinflammatory and bone remodeling markers associated with reduced cortical bone remodeling indices. Bone tissue metabolome indicated enrichment in metabolites related to amino acid transport and tryptophan catabolism in CANA-treated male mice. In contrast, CANA-treated female mice showed increases in nucleic acid metabolism. An integrOmics approach of source-matched bone tissue metabolome and bone marrow RNA sequencing indicated a positive correlation between the two omics data sets in male mice. Three clusters of transcripts and metabolites involved in energy metabolism, oxidative stress response, and cellular proliferation and differentiation were reduced in CANA-treated male mice. In conclusion, CANA affects bone metabolism mainly via the "glucose restriction state" it induces and impacts bone cell proliferation and differentiation. These findings underline the effects of SGLT2i on bone health and highlight the need to consider sex-specific responses when developing clinical treatments that alter substrate availability.